int Binary_Search(SeqList L,int key){
    int low=0,high=L.TableLen-1,mid;
    while(low<=high){
        mid=(low+high)/2;
        if(key==L.element[mid]){
            return mid;
        }else if(key<L.element[mid])
            high=mid-1;
        else if(key>L.element[mid])
            low=mid+1;
    }
    return -1;
}